Restless and alone in a brick-paved cubicle, Sarah sees a calendar before her on the wall. It is the month of October and every day is crossed out. While gazing at the image of a pumpkin patch, a dozen decayed arms punch through the wall clutching at her....
She wakes from this surreal horror in the back of a helicopter. She's reminded she is living a real nightmare, looking down over a deserted Florida city, in which they land near an abandoned harbor. She is part of a team searching for survivors of a gruesome crisis that began almost a year earlier. Something that started mysteriously and eventually collapsed human civilization. Her sometimes lover Miguel, a nerve-wracked soldier, calls for survivors on a bullhorn as they stand on the edge of the street of this now decaying town. Amid the scattered palm fronds, a newspaper blows in the death-scented wind near an early century federal building. It's big bold headline: THE DEAD WALK! (possibly one of the last papers ever printed).
The unburied and/or recently dead have returned to life. Attacking humans to devour their flesh, most of them becoming zombies, thus adding to their population. No scientist-no army, could contain or cure it. Now the only living things are the alligators, tarantulas and land crabs that scavenge remains in the streets of this city of the living dead. The hundreds of wailing hordes of dead humans turn towards the bullhorn calls and en masse, march toward the survivors instinctively like cattle, forcing the team to head back to their sanctuary.
The helicopter lands almost out of gas inside the military compound surrounded by wire fence. An army of the living dead have managed to find the post and surround the entrance gates, their numbers growing every day. Two more soldiers help secure the chopper down giving their new past times an afternoon break: Johnson, who reads the last issues of porno magazines while Torrez grows gardens of marijuana plants. John, the calm Jamaican pilot and his flask-swilling Irish buddy Bill McDermott are anxious to get on the elevator but not before urging the soldiers to fill the chopper up with gas. Sarah notices Miguel's becoming increasingly stressed and despondent. He hasn't gotten out of the chopper yet and apparently wasn't aware they even landed.
They descend into the underground sanctuary Seminole Storage Facility, where they will not see sunlight again for days. Miller is another military officer waiting below for results of the team's search. This time he can tell it was another waste of time. Everyone has to stay in the cold, lonely, clinical white cubicles of the complex while John and Bill choose to stay in one of the Winnebagos stored near the barricades. These are the corrals leading to miles and miles of caves occupied by bats... and specimen zombies, collared at an earlier time by the government. Major Cooper, the commanding officer who died earlier that morning, was buried above the complex near five other graves of men the unit has lost (four soliders and one civilian scientist). Men lost to the dangers of capturing the hostile specimen zombies corraled from the caves.
Sarah and her group meet Privates Steel and Rickles who are now in charge of the zombie corralling as Dr. Logan has requested two more guinea pig zombies for his experiments. Sarah and Miguel are asked by the two soldiers to go along with them. Though tired from the 24-hour search mission, they agree and off they go into the caves in the golf cart towards the corral.
At the corral capturing pen, Steel and Rickles both sexually harrass Sarah verbally before the shell-shocked Miguel, who is of course, oblivious. Then Steel, making his sexism clearer than ever refuses to have Sarah handle the capture and Miguel defiantly takes on the dangerous task to prove himself. He loses control of a particularly excited female specimen jeopardizing the lives of all involved. But Sarah manages to re-snare the female zombie before it can bite Rickles. The hot-tempered Steel, enraged that his buddy Rickles was almost lost because of his actions, grabs Miguel, forcing him into the clutches of a caged zombie. Sarah orders him to let him go aiming her Uzi as a possible consequence. After all is said and done, two more specimens are brought back to the lab for study. Miguel is sedated by Sarah.
In the dining hall, Dr. Ted Fisher pleads for sterile equipment to conduct proper tests on the specimens. He discusses this with Captain Rhodes, now in charge, who is also beginning to question the research that has been going on in the months the team has been sharing the facility.
Throughout the day, Dr. Matthew Logan works on captured specimens, vivisecting the ghouls' chests and removing their organs. When Sarah enters his dark operating theatre to inform him of the meeting Rhodes has scheduled, he excitedly explains that the dead do not eat flesh out of hunger, but rather motor instinct. Another corpse is under a sheet. Logan reveals this one to be only a body with its face carved away leaving only the brain exposed. With electrodes leading to a machine, Logan begins shocking the corpse back to momentary life. Sarah notices Major Coopers fatigue on the floor. And that is when Logan confesses the faceless body is his corpse and that he had switched it with a specimens for burial. He wanted a fresh corpse.
Captain Rhodes holds a 7:00 pm meeting with the remaining 12 of the group. Frustrated that he has already lost five soldiers to capture the dangerous specimens for their "research" Rhodes makes threats to shut the operation down during the meeting in the dining hall. He is aware that the unit is low on ammo, food, medical supplies and now his own men. McDermott explains that his radio equipment is outdated and this makes the soldiers think that there may indeed be survivors but that they are out of radio signal range. When Sarah gets up to leave in the middle of bickering between Steel and McDermott, Rhodes threatens to have her shot. In fact he announces anyone who challenges his orders will be shot. None of this is taken seriously by the scientists who have gotten used to threats and the soldiers' depraved harassment.
Later on, Sarah finds herself unable to sleep on the floor of the cubicle as Miguel lays in bed. By now he must be awake. He leans over and his whole chest has been surgically opened. Sarah is dreaming of course, the result of the visit to the lab earlier that day. She wakes to find Miguel is indeed up and waiting to hassle her about her fear she tries to keep a secret. She finally loses it, screaming at Miguel to leave the room. A few moments later, she wanders the hall of the complex, nearly getting caught in the middle of a scuffle between the soldiers in their bunk. She meets up with McDermott, who has been wandering the halls too. They head back to the "Ritz"-the Winnebago where he stays with John. Serving Sarah drinks, John treats her to his calm, cool Caribbean atmosphere he's created in the trailer. Not to mention a lengthy philosophical lecture on how he believes that the Creator has cursed mankind and that there can be no cure for zombification. So he urges Sarah to forget about the research and wants to leave before the soldiers lose it completely.
The next day, Sarah finds Fisher frustrated that the specimens are not accepting a meat substitute called Beef Treats. And Logan is trying to convince them that reward is the key to conditioning them. Bub is one specimen that seems to be under control. Sparing him from dissection, and instead reacquaints him with toothbrushes, razors, phones, books, tape player and even an unloaded gun. His infantile, docile behavior is unique among the zombies although Rhodes and the men witnessing this progress still think these creatures should all be destroyed.
The next day, there's another capture attempt. Miguel once again loses control of a female specimen-an old lady, unleashing her on an unsuspecting Miller who is bitten on the neck. His finger is on the trigger of his machine gun when it goes off killing Johnson in the process. Sarah destroys this lady zombiw. Miguel is then thrown into a fit of denial, attacking the priest specimen which takes a huge bite out of his forearm, forcing Miguel into hysteric shock. The priest is destroyed by Steel. Sarah runs after Miguel now fleeing towards John and Bill's area. Miller begs for Steel to end his life as he knows he would certainly become cursed with living death. Steel looms over him and blows the soldier's brains out.
John and Bill hearing Miguel's cries, wait in front of the Ritz. As Sarah draws John's machete from his belt, Miguel is overcome by a blow to the head and laid down. Sarah amputates his mutilated arm in one clean slice. After a hasty treatment, the soldiers led by Rhodes confront the three heroes, ready to destroy Miguel. John and Bill draw guns to defend his life. Rhodes declares that there will be no more experiments and that the specimens will be destroyed tomorrow. Leaving her shaken, Sarah finally breaks down and John comforts her.
Going back to the lab for supplies for Miguel, Sarah and Bill discover Johnson's decapitated head has been reanimated by Logan. Horrified, they follow Logan from the refrigerator room into Bub's room. There they witness the rewards he had stressed all along... the fresh remains of Miller and Johnson.
Just as the two realize what Logan has done Rhodes and the remaining soldiers appear behind them. The Captain drags the pleading Logan into the refrigerator to finish him off with a machine gun...amidst the dumped corpses of the military men killed in the capture attempts. He then orders the guns removed from Sarah and Bill. Then out by the corral area, ordering John to get ready to fly, Rhodes fires a bullet into the head of Fisher to make his point. Rhodes orders Sarah and Billy into the cages leading into the zombie-infested caves. John refuses to go anywhere until they are released. Then they hear the sound of the elevator...
Steel and Rickles discover someone Miguel - has taken apart the control box and that there is no way out of the complex now. They try to rewire it while Rhodes is attacked by John and knocked out. John flees with Rhodes' guns through the corral area to search for his friends in the caves.
John yells for Sarah and Billy and kills many would-be specimens in his pursuit. Rhodes finally wakes up and he and Torrez head back to find Steel and Rickles after realizing they are without weapons. A few moments later they would need any and all weapons they could get.
The deranged and suicidall Miguel had escaped and opened the front entrance gates above the complex. He is savagely eaten alive as the elevator lowered carrying the hundreds of zombies with it. The three remaining soldiers run for their lives but are attacked and dismembered one by one by ten or more ghouls at once, until the whole place is infested. Steel makes it to the complex where he finds the cowardly Rhodes had locked everyone out, so he machine guns the door and enters taking all the dead with him. He hides in a lab where Bub finds him... firing one of the weapons he had found near the refrigerator room where he found his slain master, Logan. Just as Steel reloads his weapon and has an opportunity to kill Bub from behind a door, he is reunited with the mob of zombies who've entered the room through another door. After he gets bitten on his shoulder, Steel commits suicide rather then suffer the fate of being eaten alive by the mob of zombies.
While John finally meets up with Sarah and Billy near the silo, Rhodes desperately goes for his last bit of ammunition and has a final encounter with Bub still firing his pistol (his aiming getting better) who leads him to a door where a group of the dead are waiting. In a few moments, the dead are all over the labs and storage rooms feasting on the remains of the soldiers. Rhodes is torn apart and eaten alive.
When the three survivors finally exit the silo they see at least a hundred zombies marching towards them and the helicopter...which may or may not have any gas. John and Bill cover Sarah as she runs to the chopper door. She opens it only to be greeted by another swarm of arms...
And just when you think the zombies became smart enough to hide in the chopper, Sarah wakes up on some island with John fishing in the surf and birds overhead. On her calendar, she marks out November 4th - the Day of the Dead according to Latin American folklore.